Submission #1261512

#	Time	Username	Problem	Language	Result	Execution time	Memory
1261512		SmuggingSpun	Group Photo (JOI21_ho_t3)	C++20	100 / 100	284 ms	10000 KiB

Main

#include<bits/stdc++.h>
#define taskname "C"
using namespace std;
template<class T>void minimize(T& a, T b){
	if(a > b){
		a = b;
	}
}
int n;
namespace sub1{
	void solve(){
		vector<int>a(n);
		map<vector<int>, int>f;
		for(int& x : a){
			cin >> x;
		}
		f[a] = 1;
		queue<vector<int>>q;
		q.push(a);
		while(!q.empty()){
			a = q.front();
			q.pop();
			bool flag = true;
			int init = f[a];
			for(int i = 1; i < n; i++){
				if(a[i - 1] > a[i] + 1){
					flag = false;
				}
				swap(a[i - 1], a[i]);
				if(f[a] == 0){
					f[a] = init + 1;
					q.push(a);
				}
				swap(a[i - 1], a[i]);
			}
			if(flag){
				return void(cout << init - 1);
			}
		}
	}
}
namespace sub2345{
	const int lim = 5e3 + 5;
	int dp[lim], pos[lim];
	struct FenwickTree{
		int bit[lim];
		void reset(){
			memset(bit, 0, sizeof(bit));
		}
		void update(int p, int x){
			for(; p <= n; p += p & -p){
				bit[p] += x;
			}
		}
		int get(int p){
			int ans = 0;
			for(; p > 0; p -= p & -p){
				ans += bit[p];
			}
			return ans;
		}
	};
	FenwickTree up, down;
	void solve(){
		down.reset();
		for(int i = 1; i <= n; i++){
			int x;
			cin >> x;
			down.update(pos[x] = i, 1);
		}
		memset(dp, 0x0f, sizeof(dp));
		dp[0] = 0;
		for(int r = 1; r <= n; r++){
			up.reset();
			down.update(pos[r], -1);
			int total = 0;
			for(int l = r; l > 0; l--){
				minimize(dp[r], dp[l - 1] + (total += l - pos[l] + down.get(pos[l]) + up.get(n - pos[l] + 1)));
				up.update(n - pos[l] + 1, 1);
			}
		}
		cout << dp[n];
	}
}
int main(){
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	if(fopen(taskname".inp", "r")){
		freopen(taskname".inp", "r", stdin);
	}
	cin >> n;
	if(n <= 9){
		sub1::solve();
	}
	else{
		sub2345::solve();
	}
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:88:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   88 |                 freopen(taskname".inp", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 32 / 32
• Subtask 4: 20 / 20
• Subtask 5: 36 / 36